This is what I wrote back in 16....both are Sylvania 6L6 GC.....
"I've actually read the opposite, the 387 has a bit more headroom. But essentially both are the same tube made by Sylvania. The 387 can come with 1 or 2 getters, while the 415 is always 2. According to the Boogie Board. I have a stash of Fender, Peavey branded and regular Sylvania 387s and 415s, they all sound equally great in my 2C+."
And, here's what Psychodave wrote....
"Simply put, the 387 and 415 are the same if they both have the dual top getters. They are also labeled with "6L6" at the top. Only the 387 had a single getter and middle side 6L6 labeling. Both tubes sound great.
Of course there are differences between 415's. Some have halo getters and some have foil getter (basically a halo with the center not open). There are some slight differences in performance, but I've yet to see anything definitive. I've seen some with side getters and getter flash too.
Don't forget about the Sylvania 7581a. This is a military version of the 415 and rated at 35 watts per tube. So you can have 3 different tube labels with the same looking interior structure."
